1. Field of the Invention
The present invention relates to an electrolyte supplementing apparatus for supplementing an electrolyte to matrices of cells constituting a cell lamination of a matrix-type fuel cell.
2. Description of the Prior Art
In a conventional matrix-type fuel cell, e.g., a phosphoric acid fuel cell, as shown in FIG. 2, a cell lamination 10 is formed from a plurality of cells 1 laminated one on one. Each cell 1 comprises a porous matrix 3 impregnated with an electrolyte of phosphoric acid, a fuel electrode 4a, and an oxidizing agent electrode 6a. The fuel electrode 4a comprises a fuel electrode catalyst layer 4 in contact with one surface of the matrix 3 and a gas-permeable electrode substrate 5 supporting the fuel electrode catalyst layer 4 thereon and having grooves 5a formed therein so as to act as fuel gas flowing paths. The oxidizing agent electrode 6a comprises an oxidizing agent electrode catalyst layer 6 in contact with the other surface of the matrix 3 and a gas-permeable electrode substrate 7 supporting the oxidizing agent electrode catalyst layer 6 thereon and having grooves 7a formed therein so as to act as an oxidizing agent gas flow path. Gas impermeable separators 8 are interposed between adjacent cells 1.
The fuel gas and the oxidizing agent gas are supplied as reactive gases into the cell lamination 10 to operate the fuel cells. Electrochemical reaction in each of the cells 1 produces electricity. The reaction heat generated is removed by means of a cooling medium to maintain the operation temperature.
Since the phosphoric acid contained in the matrix 3 diminishes gradually as the operation of the fuel cell progresses, the internal resistance increases as time elapses while the respective reactive gases to be supplied to the electrodes opposite to each other pass through the matrix 3 and mix with each other to generate a combustion reaction directly inside each of the cells 1. This results in damage to the electrodes with a reduction in performance or ceasing of operation of the fuel cell. In order to solve the problem, an apparatus for externally supplementing an electrolyte of phosphoric acid into the matrix 3 of a fuel cell 1 has been provided so that the phosphoric acid is continuously or periodically supplemented to the matrix 3. The present inventor has proposed an apparatus for supplementing an electrolyte to a matrix-type fuel cell in Japanese Patent Application No. 59-228228 (Japanese Patent Unexamined Publication No. 61-107667). This proposed apparatus has a structure as shown on the right side of FIG. 2.
In FIG. 2, the proposed electrolyte supplementing apparatus 11 comprises a tank assembly 13 collectively having storage tanks 12 and electrolyte supplementing conduits 14 provided between the respective storage tanks 12 and the corresponding fuel electrode supporting substrates 5 of the cells 1 of the cell lamination 10 supplement an electrolyte to the respective matrices 3 of the cells 1 through respective electrolyte supplementing channels 18 filled with a hydrophilic filler, e.g., carbon fibers. The tank assembly 13 of FIG. 2 is comprised of storage tanks 12 stacked in a plurality of layers each having two storage tanks arranged side by side. Phosphoric acid is supplied from an upper side electrolyte supply portion 15 into the storage tanks 12 for storage. The phosphoric acid supplied from the electrolyte supply portion 15 flows into the two storage tanks 12 of the uppermost layer through opening portions 16a of a partition plate 16 of the uppermost layer. When the two storage tanks 12 in the uppermost layer have been filled with the phosphoric acid to the level of a discharge portion 17 provided between the two storage tanks 12 in the uppermost layer, the phosphoric acid overflows from the discharge portion 17 of the two storage tanks 12 in the uppermost layer. The phosphoric acid then flows into the two storage tanks 12 in the next or second layer through the opening portions 16a of the partition plate 16 of the second layer, so that the storage tanks 12 in the second layer are filled with phosphoric acid. The same applies to the storage tanks 12 in all the layers of the tank assembly 13.
Each of the electrolyte supplementing ducts 14 is filled with a filler 14a of a hydrophilic material, e.g., carbon fibers, so that the phosphoric acid stored in each of the storage tank 12 is drawn by the filler 14a of the corresponding electrolyte supplementing duct 14 to flow therethrough and supplemented to the matrix 3 of the corresponding cell 1 through the electrolyte channel 18. Therefore, when the phosphoric acid is to be supplemented to the matrices 3 after operation of the fuel cell for a predetermined number of hours, the phosphoric acid is supplied from the electrolyte supply portion 15 so that all the storage tanks 12 are filled with the phosphoric acid. The stored phosphoric acid is supplemented to all the matrices 3 of the respective cells 1 through the corresponding electrolyte supplementing ducts 14.
The supplement of an electrolyte by means of the electrolyte supplementing apparatus into the matrices of the respective laminated cells 1 of the cell lamination as described above is carried out by a capillary action of the hydrophilic fillers in the respective electrolyte supplementing ducts 14 as well as by a head difference between the storage tanks 12 and the corresponding electrolyte supplementing channels 18. Accordingly, there have been problems in that the speed of displacement of the electrolyte is so low that it takes many hours to complete supplementing the matrices. Additionally, the quantity of electrolyte to be supplemented at a given time is fixed and limited by the capacity of each storage tank.